The present invention relates to an apparatus and a method for generating surface shape data on a three-dimensional object.
Recently, in the design of three-dimensional objects, computers have been extensively adopted. For example, in the design of mechanical products, three-dimensional shapes of components have been designed using the three-dimensional CAD system. Furthermore, as methods for representing a three-dimensional shapes, for example, a DMU (digital mock-up) and a three-dimensional viewer each of which, upon having built a three-dimensional model on a computer, renders the three-dimensional model as a two-dimensional image, have been put into widespread practice.
In three-dimensional computer graphics, as a technique for expressing the shape of an object, the polygon model has become widely available. The polygon model is an approach to modeling the surface of an object directly or approximately by utilizing a large number of polygons. Here, the polygon is an element for expressing a three-dimensional shape, and generally a triangle or a quadrangle. That is, when treating a three-dimensional graphic by a computer, the surface of an object is divided into minute polygons, and each of the polygons is represented by numerical data. This allows expressing the shape of the object as viewed from an optional view point. Furthermore, by increasing the number of polygons, the shape of the object can be more finely expressed.
As a related art, Japanese Unexamined Patent Application Publication No. 2-59867 discloses a method for erasing an unnecessary seam of joined portions when two convex polyhedrons are joined.
As another related art, Japanese Unexamined Patent Application Publication No. 10-111885 sets forth a management method for CAD drawings. According to this management method, in an external device, there is provided a common data storage region where common data included in N sheets of CAD drawings are stored, and a graphic data storage region where data, other than the common data, included in each of the CD graphics is stored for each of the drawings. When various graphics data is read, the common data is also read from the common data storing region.